#--
# Copyright (c) 2005-2012, John Mettraux, jmettraux@gmail.com
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#
# Made in Japan.
#++


module Ruote::Exp

  #
  # Gathering methods for merging workitems.
  #
  module MergeMixin

    # Given a list of workitems and a merge_type, will merge according to
    # the merge type.
    #
    # The return value is the merged workitem.
    #
    def merge_workitems(workitems, merge_type)

      workitems.inject(nil) do |t, wi|
        merge_workitem(workitems.index(wi), t, wi, merge_type)
      end
    end

    # Merge workitem 'source' into workitem 'target'.
    #
    # If type is 'override', the source will prevail and be returned.
    #
    # If type is 'mix', the source fields will be merged into the target fields.
    #
    # If type is 'isolate', the source fields will be placed in a separte field
    # in the target workitem. The name of this field is the child_id of the
    # source workitem (a string from '0' to '99999' and beyond)
    #
    # The 'concat' type merges hashes and concats arrays. The 'union' type
    # behaves much like 'concat', but it makes sure to remove duplicates.
    #
    # Warning: 'union' will remove duplicates that were present _before_ the
    # merge.
    #
    def merge_workitem(index, target, source, merge_type)

      return source if merge_type == 'override'

      if target == nil

        case merge_type

          #when 'mix'
             # do nothing

          when 'stack'
            source['fields'] = { 'stack' => [ source['fields'] ] }

          when 'isolate'
            source['fields'] = { index.to_s => source['fields'] }

          #when 'union', 'concat'
             # do nothing
        end

        source

      else

        case merge_type

          when 'mix'

            target['fields'].merge!(source['fields'])

          when 'stack'

            target['fields']['stack'] << source['fields']
            target['fields']['stack_attributes'] = compile_atts

          when 'isolate'

            target['fields'][index.to_s] = source['fields']

          when 'union', 'concat', 'deep'

            source['fields'].each do |k, sv|

              tv = target['fields'][k]

              if sv.is_a?(Array) and tv.is_a?(Array)
                tv.concat(sv)
                tv.uniq! if merge_type == 'union'
              elsif sv.is_a?(Hash) and tv.is_a?(Hash)
                merge_type == 'deep' ? deep_merge!(tv, sv) : tv.merge!(sv)
              else
                target['fields'][k] = sv
              end
            end
        end

        target
      end
    end

    protected

    # Inspired by the one found in ActiveSupport, though not strictly equivalent.
    #
    def deep_merge!(target, source)

      target.merge!(source) do |k, o, n|
        o.is_a?(Hash) && n.is_a?(Hash) ? deep_merge!(o, n) : n
      end
    end
  end
end